The present invention relates generally to an imaging system such as a silver-halide camera or a digital camera, and more particularly to an imaging system equipped with an electronic viewfinder that is suitably used with a small-sized image display device, especially a liquid crystal display device.
Most silver-halide cameras or digital cameras comprise means for recording images by an image pickup optical system, and a viewing optical system for checking image pickup ranges. As the image recording means, chemical reactions on a film surface are used for silver-halide cameras, and information obtained by photoelectric conversion on an electronic image pickup device such as a CCD is used for the digital cameras.
On the other hand, the viewing optical system is often designed such that a light beam from a subject side is guided to a viewer side to form an image on the viewer's retina, thereby observing the image to be picked up. This type of viewing optical system is used with or without an image pickup optical system for forming an image that records a part of the entrance side. Among the former there is typically a single-lens reflex camera. Among the latter there is typically a real image type finder that is suitable for a zoom optical system and comprises an object optical system, an image-erecting means and an eyepiece optical system. Such finders, mounted on many commercial products, are sometimes generally called optical finders.
Instead of the optical finder, many commercially available digital cameras or video cameras incorporate an electronic finder that provides a direct view of an image formed on an electronic display device such as an LCD (liquid crystal display) to enable the viewer to check the image pickup range. Many digital cameras incorporating both the optical finder and the electronic finder, too, are commercialized.
A so-called EVF (electronic viewfinder) designed to observe virtual images on LCDs through a viewing optical system has also been proposed. For conventional products incorporating such an electronic finder, there is used a display device with a display screen having a diagonal length of about 0.5 inch (about 12 mm).
In recent years, the demand for size reductions of cameras has grown.
Currently developed LCDs are smaller in size than ever before. With this, it is now required to reduce the whole size of the viewing optical system in conformity with LCD size, increase the magnification of the viewing optical system depending on size reductions of image display devices, etc.
When a reflection type display device adapted to enter light rays from its display screen therein is used as the image display device, it is required to ensure the optical path necessary for displaying images.